Proportioner, Line : This system uses a venturi pickup-type device where water passing through the unit creates a vacuum, thereby allowing foam concentrate to be picked up from an atmospheric storage container
NFPA 25 Standard for the Inspection, Testing, and Maintenance of Water-Based Fire Protection Systems, 2008 ed. https://law.resource.org/pub/us/cfr/ibr/004/nfpa.2 5.2002.pdf, (Std: Insp, Testing, and Maint of Wtr-Based Fr Prac Sys - Amer) {191 NFC}